Tempered Ammonia Injection For Gas Turbine Selective Catalyst Reduction System

ABSTRACT

The present application provides a selective catalyst reduction system for use with a combustion gas stream of a gas turbine. The selective catalyst reduction system may include an inlet positioned about the gas turbine, a combined ammonia-tempering air injection grid positioned about the inlet, and a catalyst positioned downstream of the combined ammonia-tempering air injection grid. The combined ammonia-tempering air injection grid injects air and ammonia into the combustion gas stream upstream of the catalyst.

TECHNICAL FIELD

The present application and the resultant patent relate generally to gas turbine engines and more particularly relate to tempered ammonia injection for reducing the temperature of the hot combustion gases in a gas turbine selective catalyst reduction system.

BACKGROUND OF THE INVENTION

In the combustion process of a gas turbine engine, nitrogen oxides and other types of regulated emissions are produced. Specifically, a simple cycle gas turbine emits hot flue gases that contain unacceptable levels of nitrogen oxides. One solution for reducing the overall levels of nitrogen oxide emissions is the use of a selective catalyst reduction system. Generally described, the selective catalyst reduction system adds a reductant, typically ammonia or urea, to the hot combustion gas stream before passing the combustion gas stream through a catalyst bed so as to absorb selectively the nitrogen oxides and the reducing agent. The absorbed components undergo a chemical reaction on the catalyst surface and the reaction products are desorbed. Specifically, the reactant reacts with the nitrogen oxides in the combustion gas stream to form water and nitrogen. Other types of catalysts and other types of reductants may be used.

The overall efficiency of the selective catalyst reduction system may depend in part on the temperature of the combustion gas stream. Specifically, the efficient temperature range of the selective catalyst reduction system may be relatively narrow. As such, the hot combustion gas stream generally should be cooled before reaching the catalyst bed. Moreover, careful metering and distribution of the reductant to the combustion gas stream upstream of the catalyst is required for the selective catalyst reduction system to convert and remove a sufficient level of the nitrogen oxides and the like.

SUMMARY OF THE INVENTION

The present application and the resultant patent provide a selective catalyst reduction system for use with a combustion gas stream of a gas turbine. The selective catalyst reduction system may include an inlet positioned about the gas turbine, a combined ammonia-tempering air injection grid positioned about the inlet, and a catalyst positioned downstream of the combined ammonia-tempering air injection grid. The combined ammonia-tempering air injection grid injects air and ammonia into the combustion gas stream upstream of the catalyst.

The present application and the resultant patent further provide a method of operating a selective catalyst reduction system with a combustion gas stream of a gas turbine engine. The method may include the steps of flowing the combustion gas stream into the selective catalyst reduction system, injecting a cooling air stream into the combustion gas stream about an inlet of the selective catalyst reduction system, injecting an ammonia stream into the combustion gas stream about an inlet of the selective catalyst reduction system, mixing the combustion gas stream, the cooling air stream, and the ammonia stream, and reacting the mixed stream with a catalyst.

The present application and the resultant patent further provide a combined ammonia-tempering air injection grid for use about an inlet of a selective catalyst reduction system. The combined ammonia-tempering air injection grid provides a number of air injection lances positioned about the inlet for providing a flow of air and a number of ammonia injection lances positioned about the inlet for providing a flow of ammonia. The ammonia injection lances are positioned about the air injection lances such that the flow of air cools the ammonia injection lances.

These and other features and improvements of the present application and the resultant patent will become apparent to one of ordinary skill in the art upon review of the following detailed description when taken in conjunction with the several drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a gas turbine engine showing a compressor, a combustor, a turbine, a load, and a selective catalyst reduction system.

FIG. 2 is a schematic diagram of a gas turbine engine and an alternative embodiment of a selective catalyst reduction system.

FIG. 3 is a schematic diagram of a gas turbine engine and a selective catalyst reduction system as may be described herein.

FIG. 4 is a schematic diagram of a gas turbine engine and an alternative embodiment of a selective catalyst reduction system as may be described herein.

DETAILED DESCRIPTION

Referring now to the drawings, in which like numerals refer to like elements throughout the several views, FIG. 1 shows a schematic view of gas turbine engine 10 as may be used herein. The gas turbine engine 10 may include a compressor 15. The compressor 15 compresses an incoming flow of air 20. The compressor 15 delivers the compressed flow of air 20 to a combustor 25. The combustor 25 mixes the compressed flow of air 20 with a pressurized flow of fuel 30 and ignites the mixture to create a flow of combustion gases 35. Although only a single combustor 25 is shown, the gas turbine engine 10 may include any number of combustors 25 positioned in a circumferential array and the like. The flow of combustion gases 35 is in turn delivered to a turbine 40. The flow of combustion gases 35 drives the turbine 40 so as to produce mechanical work. The mechanical work produced in the turbine 40 drives the compressor 15 via a shaft and an external load such as an electrical generator and the like.

The gas turbine engine 10 may use natural gas, various types of syngas, liquid fuels, and/or other types of fuels and blends thereof. The gas turbine engine 10 may have different configurations and may use other types of components. Other types of gas turbine engines also may be used herein. Multiple gas turbine engines, other types of turbines, and other types of power generation equipment also may be used herein together.

The gas turbine engine 10 also may include a selective catalyst reduction system 45. The selective catalyst reduction system 45 may be positioned downstream of the turbine 40. As described above, the selective catalyst reduction system 45 may include a catalyst 50 therein so as to react with the combustion gas stream 35. The catalyst 50 may be of conventional design and may be manufactured from suitable carrier and active catalytic components. Different types of catalysts 50 may be used herein. The catalyst 50 may have any suitable size, shape, or configuration. The selective catalyst reduction system 45 may extend from an inlet 55 to a stack 60 or other type of exhaust. An ammonia injection grid 65 may be positioned about the catalyst 50 so as to inject a reductant such as ammonia into the combustion gas stream 35. The ammonia injection grid 65 may be in communication with an ammonia source 70. The ammonia injection grid 65 may be in communication with the ammonia source 70 via an extensive piping system to produce an adequate ammonia distribution into the incoming combustion gas stream 35. The stack 60 or other type of exhaust may be positioned downstream of the catalyst 50.

The selective catalyst reduction system 45 also may include a tempering air system 75. The tempering air system 75 may reduce the temperature of the combustion gas stream 35 before the stream 35 reaches the catalyst 50. The tempering air system 75 may include a tempering air grid 80 positioned about the inlet 55 of the selective catalyst reduction system 45 and upstream of the ammonia injection grid 65 and the catalyst 50. The tempering air grid 80 may be in communication with a source of ambient air 20 via a tempering air fan 85 or other type of air movement device. A gas mixer 90 may be positioned downstream of the tempering air grid 80. The gas mixer 90 may include a series of baffles and the like. The gas mixer 90 may mix the incoming combustion gas stream 35 and the ambient air 20 so as to obtain an adequate temperature distribution. The now cooled flow then may flow past the ammonia injection grid 65 and the catalyst 50 for reaction therewith.

FIG. 2 shows the gas turbine engine 10 with an alternative selective catalyst reduction system 95. In this example, the selective catalyst reduction system 95 may not use the tempering air system 75. Instead, the selective catalyst reduction system 95 may position the ammonia injection grid 65 about the inlet 55 of the selective catalyst reduction system 95 at a distance to the catalyst 50. By injecting the ammonia directly into the hot combustion gas stream 35 as it exits the turbine 40, the ammonia injection grid 65 may accommodate the complex gas flow patterns exiting the turbine 40. The selective catalyst reduction systems described herein are for the purpose of example only. Other types of selective catalyst reduction systems and system components may be in use.

FIG. 3 shows the gas turbine engine 10 with a selective catalyst reduction system 100 as may be described herein. The selective catalyst reduction system 100 may extend from an inlet 110 positioned about the turbine 40 to a stack 120 or other type of exhaust at a downstream end thereof. The selective catalyst reduction system 100 may have any suitable size, shape, configuration, or capacity.

The selective catalyst reduction system 100 may include a catalyst 120. The catalyst 120 may be of conventional design. The catalyst 120 may be positioned within the selective catalyst reduction system 100 at a distance downstream from the inlet 110.

The selective catalyst reduction system 110 may include a combined ammonia-tempering air injection grid 140. The combined ammonia-tempering air injection grid 140 may be positioned about the inlet 110 of the selective catalyst reduction system 100 in the path of the combustion gas stream 35. The combined ammonia-tempering air injection grid 140 may be in communication with a flow of ambient air 20 via a tempering air fan 150 or other type of air movement device. The tempering air fan 150 may have any suitable size, shape, or configuration. The combined ammonia-tempering air injection grid 140 may include a number of air injection lances 160 positioned about the inlet 110. The air injection lances 160 may have any suitable size, shape, or configuration. Any number of the air injection lances 160 may be used. The air injection lances 160 may be in communication with the ambient air 20 or other type of air source from the tempering air fan 150 via one or more tempering air conduits 170. The tempering air conduits 170 may have any suitable size, shape, or configuration. Other components and other configurations may be used herein.

The combined ammonia-tempering air injection grid 140 also may be in communication with a flow of ammonia 180 or other type of reductant from an ammonia source 190. The combined ammonia-tempering air injection grid 140 may include a number of ammonia injection lances 160 positioned about the inlet 110. The ammonia injection lances 200 may have any suitable size, shape, or configuration. Any number of the ammonia injection lances 200 may be used. The ammonia injection lances 200 may be in communication with the flow of ammonia 180 via one or more ammonia conduits 210. The ammonia conduits 210 may have any suitable size, shape, or configuration. One or more pumps (not shown) or other type of fluid moving device also may be used herein.

The injection air lances 160 and the ammonia injection lances 200 may be separate structures with dedicated spray nozzles and/or dual fluid spray nozzles also may be used. By combining the flows of air and ammonia, the ambient air flow 20 may cool the ammonia injection lances 200 so as to thermally protect the ammonia injection lances 200 from the hot combustion gas stream 35. Specifically, the ambient air flow 20 serves to cool the ammonia injection lances 200 such that the combined ammonia-tempering air injection grid 140 may be positioned about the inlet 110 instead of downstream of an air injection grid for thermal protection. Moreover, by positioning the combined ammonia-tempering air injection grid 140 at the inlet 110, the hot combustion gases 35 may evaporate the flow of ammonia 180 in the flow of the ambient air 20 to ammonia vapor upstream of the catalyst for good overall distribution. Other components and other configurations may be used herein.

A gas mixer 220 may be positioned downstream of the combined ammonia-tempering air injection grid 140. The gas mixer 220 may include a series of baffles and the like. The gas mixer 220 may have any suitable size, shape, or configuration. The gas mixer 220 may mix and blend the flow of ambient air 20 and the flow of ammonia 180 in the combustion gas stream 35. The gas mixer 220 provides the combustion gas stream 35 with an adequate temperature distribution as well as an adequate ammonia distribution. Other components and other configurations may be used herein.

FIG. 4 shows an alternative embodiment of a combined ammonia-tempering air injection grid 230. In this example, the ammonia conduits 200 may merge with the tempering air conduits 170 into one or more merged flow conduits 240 for use with one or more merged flow lances 250. As a further alternative, the respective conduits and lances may be co-axial and lead to the dual fluid spray nozzles. As above, the ambient air flow 20 serves to cool the ammonia components such that the combined ammonia-tempering air injection grid 140 may be positioned about the inlet 110 of the selective catalyst reduction system 100 instead of downstream of an air injection grid. Other components and other configurations may be used herein.

In use, the hot combustion gas stream 35 from the turbine 40 enters the inlet section 110 of the selective catalyst reduction system 100. The combustion gas stream 35 flows past the combined ammonia-tempering air injection grid 140 as the injection lances 160, 200 inject the flows of ambient air 20 and ammonia 180. The flows of ambient air 20 protect the ammonia injection lances 200 while cooling the combustion gas stream 35. Once injected, the flow of ammonia 180 may evaporate in the combustion gas stream 35 into ammonia vapor upstream of the catalyst 130. The gas mixer 220 promotes good mixing of the streams with a substantially uniform temperature and ammonia distribution about the catalyst 130.

The combined ammonia-tempering air injection grid 140 further avoids the need for separate air injection grids and ammonia injection grids and the associated piping. Moreover, specific spray nozzles designed to accommodate the flow patterns of the combustion gas stream 35 may be avoided. The combined ammonia-tempering air injection grid 140 thus cools the combustion gas stream 35 from the turbine 40 to within an appropriate temperature range for efficient use with the catalyst 130 in a simplified, less expensive design.

It should be apparent that the foregoing relates only to certain embodiments of the present application and the resultant patent. Numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the invention as defined by the following claims and the equivalents thereof. 

I claim:
 1. A selective catalyst reduction system for use with a combustion gas stream of a gas turbine, comprising: an inlet positioned about the gas turbine; a combined ammonia-tempering air injection grid positioned about the inlet; and a catalyst positioned downstream of the combined ammonia-tempering air injection grid; wherein the combined ammonia-tempering air injection grid injects air and ammonia into the combustion gas stream upstream of the catalyst.
 2. The selective catalyst reduction system of claim 1, wherein the combined ammonia-tempering air injection grid comprises a plurality of air injection lances.
 3. The selective catalyst reduction system of claim 2, wherein the combined ammonia-tempering air injection grid comprises an air source in communication with the plurality of air injection lances.
 4. The selective catalyst reduction system of claim 2, wherein the combined ammonia-tempering air injection grid comprises one or more air conduits in communication with the plurality of air injection lances.
 5. The selective catalyst reduction system of claim 2, wherein the combined ammonia-tempering air injection grid comprises one or more fans in communication with the plurality of air injection lances.
 6. The selective catalyst reduction system of claim 2, wherein the combined ammonia-tempering air injection grid comprises a plurality of ammonia injection lances.
 7. The selective catalyst reduction system of claim 6, wherein the plurality of plurality of ammonia injection lances is positioned about the plurality of air injection lances.
 8. The selective catalyst reduction system of claim 6, wherein the flow of air from the plurality of air injection lances cools the plurality of ammonia injection lances.
 9. The selective catalyst reduction system of claim 6, wherein the combined ammonia-tempering air injection grid comprises an ammonia source in communication with the plurality of ammonia injection lances.
 10. The selective catalyst reduction system of claim 6, wherein the combined ammonia-tempering air injection grid comprises one or more ammonia conduits in communication with the plurality of ammonia injection lances.
 11. The selective catalyst reduction system of claim 1, further comprising a gas mixer positioned downstream of the combined ammonia-tempering air injection grid.
 12. The selective catalyst reduction system of claim 1, wherein the combined ammonia-tempering air injection grid comprises an air conduit and an ammonia conduit.
 13. The selective catalyst reduction system of claim 12, wherein the air conduit and the ammonia conduit comprise a merged flow conduit.
 14. The selective catalyst reduction system of claim 13, wherein the merged flow conduit is in communication with a plurality of merged flow lances.
 15. A method of operating a selective catalyst reduction system with a combustion gas stream of a gas turbine engine, comprising: flowing the combustion gas stream into the selective catalyst reduction system; injecting a cooling air stream into the combustion gas stream about an inlet of the selective catalyst reduction system; injecting an ammonia stream into the combustion gas stream about an inlet of the selective catalyst reduction system; mixing the combustion gas stream, the cooling air stream, and the ammonia stream; and reacting the mixed stream with a catalyst.
 16. A combined ammonia-tempering air injection grid for use about an inlet of a selective catalyst reduction system, comprising: a plurality of air injection lances positioned about the inlet for providing a flow of air; and a plurality of ammonia injection lances positioned about the inlet for providing a flow of ammonia; wherein the plurality of ammonia injection lances are positioned about the plurality of air injection lances such that the flow of air cools the plurality of ammonia injection lances.
 17. The combined ammonia-tempering air injection grid of claim 16, further comprising an air source and a fan in communication with the plurality of air injection lances.
 18. The combined ammonia-tempering air injection grid of claim 16, further comprising an ammonia source in communication with the plurality of ammonia injection lances.
 19. The combined ammonia-tempering air injection grid of claim 16, further comprising an air conduit and an ammonia conduit.
 20. The combined ammonia-tempering air injection grid of claim 19, wherein the air conduit and the ammonia conduit comprise a merged flow conduit. 